Cross-talk measurement apparatus with near-end compensation
First Claim
1. In an instrument for measuring a cross-talk response in a pair of transmission lines, a method for removing undesired cross-talk effects from at least one selected location along said pair of transmission lines, comprising:
- (a) generating stimulus signals to one of said pair of transmission lines;
(b) receiving cross-talk signals from another of said pair of transmission lines and digitizing said cross-talk signals as a pulse-response time record wherein said cross-talk signals are produced in response to said stimulus signals;
(c) constructing an undesired-response time record from said pulse-response time record containing only said undesired cross-talk effects corresponding to said selected location;
(d) calculating a first frequency domain representation of said pulse-response time record and a second frequency domain representation of said undesired-response time record; and
(e) calculating said cross-talk response by subtracting said second frequency domain representation from said first frequency domain representation.
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Accused Products
Abstract
A pulse-based cable crosstalk measurement instrument provides near-end cross talk (NEXT) information for characterizing the performance of local area network (LAN) cable systems. Accuracy of the cross-talk measurement is enhanced by measuring and mathematically removing the cross-talk effects of the near-end connector. Accuracy of the cross-talk measurement is further enhanced by conducting the cross-talk measurement with pulses of differing pulse widths selected to have increased pulse energy in frequency ranges of interest. A composite cross-talk response using the individual cross-talk responses of the individual pulse widths concatenated together is created and then compared with an industry-standard pass fail limit to provide a pass-fail decision on a LAN cable test system under test.
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Citations
25 Claims
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1. In an instrument for measuring a cross-talk response in a pair of transmission lines, a method for removing undesired cross-talk effects from at least one selected location along said pair of transmission lines, comprising:
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(a) generating stimulus signals to one of said pair of transmission lines; (b) receiving cross-talk signals from another of said pair of transmission lines and digitizing said cross-talk signals as a pulse-response time record wherein said cross-talk signals are produced in response to said stimulus signals; (c) constructing an undesired-response time record from said pulse-response time record containing only said undesired cross-talk effects corresponding to said selected location; (d) calculating a first frequency domain representation of said pulse-response time record and a second frequency domain representation of said undesired-response time record; and (e) calculating said cross-talk response by subtracting said second frequency domain representation from said first frequency domain representation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In an instrument for measuring a cross-talk response in a local area network cable, a method for removing cross-talk effects of a near-end connector, comprising:
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(a) generating stimulus signals to a first selected wire pair within said near-end connector; (b) receiving cross-talk signals from a second selected wire pair within said near-end connector and digitizing said cross-talk signals as a pulse-response time record wherein said cross-talk signals are produced in response to said stimulus signals; (c) constructing an undesired-response time record from said pulse-response time record containing only said cross-talk effects of said near-end connector; (d) calculating a first frequency domain representation of said pulse-response time record and a second frequency domain representation of said undesired-response time record; and (e) calculating said cross talk response by subtracting said second frequency representation from said first frequency representation. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. In a pulse-based instrument for measuring a cross-talk response, a method for increasing signal energy at a set of selected frequency ranges, comprising:
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(a) generating a series of stimulus pulses to a first transmission line within local area network cable according to a set of pulse widths wherein each of said pulse widths is selected to provide a desired amount of pulse energy at said corresponding frequency ranges; (b) receiving cross-talk signals from a second transmission line within said local area network cable and digitizing said cross-talk signals as a set of time records wherein each time record corresponds with a predetermined pulse width and said cross-talk signals are produced in response to said stimulus pulses; (c) calculating a set of cross-talk responses corresponding to each of said set of said time records; and (d) concatenating portions of said cross-talk responses corresponding with said selected frequency ranges to construct said cross-talk response between said first and second transmission fines. - View Dependent Claims (17, 18, 19)
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20. An instrument for measuring a cross-talk response in a pair of transmission lines in a local area network cable while removing undesired cross-talk effects from at least one selected location along said pair of transmission lines, comprising:
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(a) a near-end connector coupled to said pair of transmission lines; (b) a pulse generator for generating stimulus pulses in one of said pair of transmission lines; (c) a digitizer coupled to said near-end connector for receiving cross-talk signals from another of said pair of transmission lines and producing a pulse-response time record of said cross-talk signals wherein said cross-talk signals are produced in response to said stimulus pulses; and (d) a microprocessor coupled to said digitizer for receiving said time record, wherein said microprocessor calculates a cross-talk response of said time record, and mathematically removes said undesired cross-talk effects from said cross-talk response. - View Dependent Claims (21, 22, 23)
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24. An pulse-based instrument for measuring a cross-talk response in a pair of transmission lines in a local area network cable, comprising:
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(a) a near-end connector coupled to said pair of transmission lines; (b) a pulse generator coupled to said near-end connector for generating stimulus pulses in one of said pair of transmission lines wherein said stimulus pulses comprise a plurality of pulse widths chosen to provide sufficient energy in a set of frequency ranges that correspond with said plurality of pulse widths; (c) a digitizer coupled to said near-end connector for receiving cross-talk signals from another of said pair of transmission lines, and producing a pulse-response time record of said cross-talk signals for each pulse width wherein said cross-talk signals are produced in response to said stimulus pulses; and (d) a microprocessor coupled to said pulse generator for selecting said pulse widths and to said digitizer for receiving said pulse-response time records, wherein said microprocessor calculates a cross-talk response of each of said time records, mathematically removes the undesired cross-talk effects of said near-end connector, and constructs said cross-talk response by concatenating selected portions of each frequency representation that corresponds with each of said sets of pulse widths and frequency ranges. - View Dependent Claims (25)
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Specification